visa change from visitor to J1

Hello, do you know if I enter the united states as visitor, Can I apply for J1 visa inside the united states or I must go back to canada and cross de boarder again ? thanks

You don't need a visa for J-1 as a Canadian citizen, you get the DS-2019 from wherever you're going and present it as the POE. Not sure if you can change status, but colleges don't recommend it.

Have a read of this: http://www.uscis.gov/files/form/i-539instr.pdf